Kinetics and mechanism of indigo carmine-acidic iodate reaction. An indicator reaction for catalytic determination of Ru(III) ion
✍ Scribed by G. K. Muthakia; S. B. Jonnalagadda
- Publisher
- John Wiley and Sons
- Year
- 1989
- Tongue
- English
- Weight
- 637 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0538-8066
No coin nor oath required. For personal study only.
✦ Synopsis
A kinetic study of uncatalyzed and Ru(II1) catalyzed oxidation of indigo carmine(1C) (disodium 3,3'-dioxobi-indolin-2,2'-ylidene-5,5'-disulphonate) by iodate ion in aqueous sulphuric acid solution is reported. The uncatalyzed reaction order was found to be four; one each with respect to IC and iodate ion and second order with H' ion. The Ru(II1) catalyzed reaction was of fifth order, second order with respect to H' and first order with respect to reductant, oxidant, and catalyst. Stoichiometric ratios of both reactions were the same with a 3 : 2 reductant-oxidant ratio. In both uncatalyzed and catalyzed reactions isatin-5-monosulphonic acid (2,3-dioxoindoline-5-sulphonic acid) was observed as the oxidation product. Rate constants for both the reactions are reported. Reaction mechanisms consistent with the experimental data are suggested.
Further, a fixed time method is described for the determination of Ru(III), based on its ability to catalyze the oxidation of IC by acidic iodate. Using [H'] 2.2511.1, [iodate] 1.00 x W 3 M and [IC] 5.0 x 10-5M, in presence of Ru(III), the reaction followed first order kinetics with respect to IC. The interference of various cations, neutral salts, and potassium iodide on the determination of Ru(II1) was studied using synthetic mixtures. The selectivity of the method and the recommended procedure are described.